[triod750]

so, imho, what we are doing here is a nice/funny game... but it is all except science and the fact we are lucky that nothing explode doen't elevate that at science level... an example: the catode resistance should be, as from tube C3g manufacturer application specs, 180Ohm.... inside the LD Mk2 is 680Ohm, and probably has the same value inside the Mk3 and Mk4 too, not exactly the same thing isn't it?

You are completely right in that we, or at least I, don't discuss at science level. We, or I, just discuss how to get the best out of Little Dot without breaking the bank.

But real knowledge isn't just to know things, it's the combination of both knowing and having experience. In this community we are trying to help each other with this. Maybe we gather more experience than knowledge .

I welcome science too, even when it is above my understanding.

 

[mordy]

all correct but maybe appliable only at the game we are playing here inside... plug and play this or that because is "compatible", more or less, and the ampli seems will not be explode... good, I'm doing the same and I like it

... but there outside there are also people that build amplifier, or pre-amplifire or whatever, going trough a project that is calculated considering specific values from data-sheet were, for example, values like Gm or Vkf has a meaning and has to be taken in serious consideration... so probably a good tube and an end-of-the life one are not the same, otherwise people, in industry for example, or military application, will never replace tube

so, imho, what we are doing here is a nice/funny game... but it is all except science and the fact we are lucky that nothing explode doen't elevate that at science level... an example: the catode resistance should be, as from tube C3g manufacturer application specs, 180Ohm.... inside the LD Mk2 is 680Ohm, and probably has the same value inside the Mk3 and Mk4 too, not exactly the same thing isn't it?

When you speak to a tube amplifier designer - any such designer - they will tell you that it is all about making compromises. This is not an exact science.
Just sit back, relax, and enjoy what you are listening to, whether you are listening to your amp or listening to the music...
Both listening methods are valid, and I suspect that we all are doing both at different times.

 

[triod750]

When you find something that sounds good in your amp you can stop there and call it a day. You have what you need.

But you don't have to. I am now listening to a combination that is very pleasing. For input I use a Sittard made Philips E80CC, inspired by @gibosi a long while back in this thread. As output tubes I am using GEC made A2293 - four of them. Each of these equals half a 6AS7g (or 6080). They are single triodes while 6N6P are dual/double triodes. That is why I am using four. All these tubes needs adapters and external power supply. You don't need these tubes to enjoy your music. But I enjoy using them to enjoy my music.

Before trying these, I used a Ken-Rad made 6N7 for input and two Sylvania 6BL7GT for output. I enjoyed that combination too. Do I recommend it? I recommend you to enjoy your music in a way that makes you happy.

Little Dot is a very flexible amp. That much can be said.

Edit: I made a mistake; this E80CC isn't made in Sittard (since they didn't make that tube type) but in Heerlen. I mixed it up with another tube I have. Thank you @gibosi .

 

[lupoal]

Have you pulled the top cover off to see what the actual rating is on the transformer? If you could post a picture of the label that would be great for the thread as we already have a few other models.

here we are, at the end I've done a set of measurement using the original set of tubes from factory...
first of all the picture about the transformer, is somebody is able to traslate from chinese would be nice... well number are self-explaining

and how wires are connected inside the LD2 ... input, those two black-red in between are joined togher to reach the 240Vac, the Green is to OVdc at the output of the bridge whic is connected to ground, so porobaly the transofermer is shielded

and output, heaters ... a is twisted with b... c is twisted with d... the black wire is the connection to elevate the heater voltage... those connetion are all Vac and, in theory, sould be around 6,3V +/- 5% (maximun /-10% but not valid for all tubes models) (sorry... blu mean blue ... and verde means green)

while checking for connection I've seen that the transformer has been quite poorely assembled... so I squeezed the external mtal part to avoid potential vibrations (that can cause electrical noise in the circuits that can damage audio quality)

now the funny part... with the original tubes, so no overload because of tube not considered in the original project, I've measured, with constant voltage from the wall of 220Vac ---> 144Vac at the output instead of 151,25Vac (from (165/240)*220)... not a big gap but 5% lower then target...

then I measured the values at tubes...

so, before somebody will start telling me "take it easy" or "it sounds good so who care" consider that (let's forget for a moment potential problems about shorter tube life)... too low voltage at heaters means lower temperature... that means lower level of electron emitted by katode... that means lower Gm... that means lower dinamic range, lower sound quality

the reason why the transformer has so poor quality is simple, the transformer is the most expensive part inside a tube amplifier... so our chinese friends declared some values and installed something that can't reach those values saving money... oh well, no, for sure it is only my unit that is under-powered

anyway... I'm thinking to remove that transformer and realize an external "brick" with better transformer and two regulated linear power stage to DC supply heaters (from Amazon roughly 10 bucks each), deleting in this way any variation/fluctuation in the 6,3V because of the Vac fluctuations

in the mean time I switched to some other tube well sounding but not so expensive

 

[TrollDragon]

@lupoal thanks for the transformer label, too bad they didn't print the current output on it like they did the others.

Yes your best be might be a pair of external regulators to provide a solid 6.3V heater supply directly to the tube sockets. I would have a look at the board to make sure the filament pins don't go anywhere else before you unsolder the wires from the transformer I think the black wire for the input pair goes to the board someplace.

Edit Add: They do take the power for the LED from the input heater wires.

 

[triod750]

I have previously said that my output 6SN7/6H12C might sound a little more 'on their toes' (don't remember how I worded it) with external heating power, although they don't need it. I haven't checked what transformer I have. The only parts I have removed from my amp is all the brass. This gives better ventilation. I guess I have the same chassis as MK9.

 

[lupoal]

...
Edit Add: They do take the power for the LED from the input heater wires.

... that's another doubt I have... the 6N6P heaters are connected directly to the transformer, the 5654 winding on the transformer has a center tap that is connected to +Vdc to pull-up the heater voltage... I have no idea where this LED is connected , I will open the LD again to try to map it... but it's really crowdy

 

[triod750]

Before buying my MKIVSE I was lent a MKIII for a few months. I was told that the MKIV was the same amp with some better components. Then sombody told me that this MKIVSE was for sale as used. I bought it and compared them for a while before returning the MKIII. I liked my MKIV much better, thought it had a fuller, more relaxed sound but told myself that it was only in my head since it was mine.

Anyway, I just removed the transformer cover and found a toroidal transformer underneith upon a 'tray' with flanges, tightly bolted to the chassis. The tray is also screwed to the chassis and the transformer cover is then screwed to the flanges of that 'tray'. This seems very well made. The text on the transformer as follows:

MKIV Se A few chinese 'letters' here.

I/P 0V----------220V RED------RED

0/P 3,2V---0V---3,2V BLU--BLK--BLU

0V-----6,6V GRN-----GRN

0V----175V YEL------YEL

20160428

Sorry, still no camera. But I am sharing, old school.

 

[TrollDragon]

I can't find the picture of the label in my MK IV (it was probably lost in the forum upgrade), but I do believe mine had current ratings on it as well as the voltage.

I'll have to dig through the pictures on my PC.

 

[triod750]

There are currently no ratings...

But you have a toroidal transformer too?

 

[triod750]

With my external heater power supply and additional adapters I have been able to experiment with a lot of not so common tube combinations. One of the tubes that I have liked since I first used it is the Melz 6H8C/6N8S. This is a Soviet version of 6SN7GT that I have used as output tubes. It is very transparent but a bit too much on the bright side of neutral. I have now revisited this old favourite using other input tubes. First I tried a Tung-Sol 6N7GT/G and this tamed the brightness without detracting from transparency. It made for relaxed listening. Then I tried Philips E80CC which also compliments the Melz 6H8C well, while being a little livelier than the Tung-Sol combination. Right now I'm listening to something unexpected; I am using a Sylvania 6BL7GT as input. It's probably a far fetched combination but it sounds really good too. The downside with this last combination is the slightest of hum in silent passages. They are better used as output tubes but the experiment was interesting.

Before this, I tried another Tung-Sol combination; 6N7GT/G for input and 6080 WA for output. The outcome was relaxed and neutral sound that might become a little boring in the long run. While the sound was more than acceptable the heat from these 6080 tubes (an electrical equivalent to 6AS7G) is a bit too much in our amps in my opinion. This isn't based on knowledge, I am just trying to avoid being careless. But four A2293 tubes - two per channel in adapters - runs cooler than 6080 in my amp and sounds a lot better in my opinion with the 'right' input tubes. They are single triodes while 6080/6AS7G are double triodes. 2xA2293 is about equal to one 6080/6AS7G.

But I get a long way towards that sound quality using 6BX7GT or 6BL7GT as output. These latter tubes run much cooler which is good and relevant during the summer months.

Just wanted to share some impressions...

 

[mordy]

With my external heater power supply and additional adapters I have been able to experiment with a lot of not so common tube combinations. One of the tubes that I have liked since I first used it is the Melz 6H8C/6N8S. This is a Soviet version of 6SN7GT that I have used as output tubes. It is very transparent but a bit too much on the bright side of neutral. I have now revisited this old favourite using other input tubes. First I tried a Tung-Sol 6N7GT/G and this tamed the brightness without detracting from transparency. It made for relaxed listening. Then I tried Philips E80CC which also compliments the Melz 6H8C well, while being a little livelier than the Tung-Sol combination. Right now I'm listening to something unexpected; I am using a Sylvania 6BL7GT as input. It's probably a far fetched combination but it sounds really good too. The downside with this last combination is the slightest of hum in silent passages. They are better used as output tubes but the experiment was interesting.

Before this, I tried another Tung-Sol combination; 6N7GT/G for input and 6080 WA for output. The outcome was relaxed and neutral sound that might become a little boring in the long run. While the sound was more than acceptable the heat from these 6080 tubes (an electrical equivalent to 6AS7G) is a bit too much in our amps in my opinion. This isn't based on knowledge, I am just trying to avoid being careless. But four A2293 tubes - two per channel in adapters - runs cooler than 6080 in my amp and sounds a lot better in my opinion with the 'right' input tubes. They are single triodes while 6080/6AS7G are double triodes. 2xA2293 is about equal to one 6080/6AS7G.

But I get a long way towards that sound quality using 6BX7GT or 6BL7GT as output. These latter tubes run much cooler which is good and relevant during the summer months.

Just wanted to share some impressions...

One reason the 6080 runs hotter is that each tube is 2.5A for a total of 5A, whereas A2293 is 0.95A for a total of 3.8A. Nevertheless, it appears to me that the 6080 runs hotter than the 6AS7 which is an equivalent but has a larger envelope.
IMHO you will not run into problems if you use external fan cooling.

 

[triod750]

One reason the 6080 runs hotter is that each tube is 2.5A for a total of 5A, whereas A2293 is 0.95A for a total of 3.8A. Nevertheless, it appears to me that the 6080 runs hotter than the 6AS7 which is an equivalent but has a larger envelope.
IMHO you will not run into problems if you use external fan cooling.

I agree with you that 6080 subjectively seems hotter than 6AS7G and that external fan cooling could prevent problems. However, long term effects from excessive heat might shorten the life of components. (I might worry too much about that. I can still hold my hand on transformer cover or on the chassis without being bothered). That wouldn't matter that much if I thought that the sound quality difference from using 'hotter tubes' was rewarding but I don't. Not in my amp. I don't doubt that those hotter tubes can give better reward in amps designed for them. But for me the A2293 sounds better and are cooler.

 

[hamcha]

Amperex 6AK5/E95 (Orange Globe)

Really wide sound stage but still very intimate. I catch myself turning my head hearing things outside of my headphones but quickly realize that the sound is coming from the headphones. COOL!!! Clear upfront trebles/highs & vocals. Moderate punchy bass and low end.

FOR REFERENCE - Adding this as I have not seen much if any about these tubes and thought it might be worthy contribution. I am a noobie so take this will a grain of salt. Also, I just got my LD1+. I love this tube amp and really brings so much to the listening experience. I have been listening to E95 tubes which are highly rated (Voskhod 6ZH1P-EV , Mullard M8100 / CV4010) but recently switched to Amperex 6AK5/E95 (Orange Globe) that came with the used LD1+ and had to reply to this thread with above notes. Really enjoying these tubes.. Thanks.

 

[gibosi]

Amperex 6AK5/E95 (Orange Globe)

Really wide sound stage but still very intimate. I catch myself turning my head hearing things outside of my headphones but quickly realize that the sound is coming from the headphones. COOL!!! Clear upfront trebles/highs & vocals. Moderate punchy bass and low end.

FOR REFERENCE - Adding this as I have not seen much if any about these tubes and thought it might be worthy contribution. I am a noobie so take this will a grain of salt. Also, I just got my LD1+. I love this tube amp and really brings so much to the listening experience. I have been listening to E95 tubes which are highly rated (Voskhod 6ZH1P-EV , Mullard M8100 / CV4010) but recently switched to Amperex 6AK5/E95 (Orange Globe) that came with the used LD1+ and had to reply to this thread with above notes. Really enjoying these tubes.. Thanks.

It's been many years since I had my LD, but I am not sure that Amperex actually made the 6AK5. Yours might be Mullard?